Simple amine compounds are known to provide neutralizing, dispersant and hardening properties when added to coatings, mineral slurries and epoxy formulations. Methods for simple amine compound manufacture are well-documented and known in the art, and when the goal is to prepare primary amines, the preferred routes often involve intermediate nitro alcohol compounds. For various reasons, it would be advantageous to have compounds with more than one amino group and low volatile organic compound (“VOC”) content.
Volatile organic compounds are organic chemical compounds that have high enough vapor pressures under normal conditions (i.e., 1 atmosphere and 25° C.) to significantly vaporize and enter the atmosphere. They include a variety of chemicals, many of which have adverse health effects, and are emitted by a wide variety of products including but not limited to: paints and lacquers, paint strippers, cleaning supplies, pesticides, building materials and furnishings, office equipment such as copiers and printers, correction fluids and carbonless copy paper, graphics and craft materials including glues and adhesives, permanent markers, and photographic solutions. Minimization of VOC content has become the focus of public attention as well as government regulation.
Processes for the manufacture of the intermediate nitro alcohol compounds, are known and typically involve nitro aldol reaction (Henry Reaction) between nitroalkanes and aldehydes. There has been occasional reference to the preparation of dinitro alcohols involving a tandem Michael addition and Henry reaction of a nitroalkane with an α,β-unsaturated aldehyde. For example, see “Secondary dinitro alcohols,” Smith, Curtis W. (Shell Development Co.) 1949, and U.S. Pat. No. 2,475,996, which describe the manufacture of the nitro alcohol 2,5,6-trimethyl-2,6-dinitro-3-heptanol. This nitro alcohol is also prepared as an intermediate to making a vasopeptidase inhibitor, as discussed in Efficient Asymmetric Synthesis of the Vasopeptidase Inhibitor BMS-189921 by Janak Singh et al., Org. Lett. (2003), 5, 17, 3155-3158. In addition, manufacture of the nitro alcohol compound 2,6-dinitro-5-phenyl-heptan-3-ol has been described in David St. Clair Black et. al. Australian Journal of Chemistry, 1976, 29(11), 2511. As is also well-established, nitro alcohol compounds may be readily converted to the aminoalcohol compounds by hydrogenation with hydrogen over a suitable catalyst, for example Raney nickel or a platinum- or palladium-based catalyst (Pt or Pd in elemental form or as oxides, with or without supports, e.g., carbon). Those skilled in the art are also aware that other reducing agents which will reduce nitroalkanes to primary amines include metal/acid combinations, e.g., iron/acetic acid; and aluminum hydrides. The preferred reducing agents include hydrogen gas in combination with any of the following catalysts: Raney nickel, platinum or palladium.
Diamino alcohol compounds and their uses, on the other hand, are not currently represented in the prior art.
Amino alcohols such as 2-amino-2-methyl-1-propanol (“AMP”) are used in aqueous based paint formulations as neutralizing amines which effectively co-disperse pigments. In many geographies paint manufacturers are facing additional regulations to reduce the VOC content of their formulations and consumer preference is driving the development of low odor paint formulations. Neutralizing amines such as AMP are 100% volatile according to a modified EPA Test Method 24 and, when used in a low VOC paint formulation, the amine odor of AMP becomes more noticeable. Two options as neutralizers that are by definition no VOC contributors are ammonia and inorganic bases such as KOH. Ammonia, while an efficient neutralizer, has a very strong odor and is, therefore, unsuitable for use in low odor paint formulations. The use of inorganic bases such as KOH, produce coatings with poor scratch and mar resistance. Additionally, neither ammonia nor the inorganic bases have the ability to aid in the dispersion of pigments in the formulation.
There is a need for efficient organic neutralizing amino alcohols which are effective co-dispersants with low or no VOC and have very low or no amine odor. The novel diamino alcohol compounds described above and in further detail hereinafter, are excellent low odor multifunctional amines with the benefit of having no or low VOC as measured by a method similar to the EPA Test Method 24 which is the required method for measuring the VOC of a finished paint formulation. An additional benefit of these products is that by design they can only contain primary amine functional groups which cannot generate toxic N-nitroso compounds.